The invention relates generally to sporting goods and recreational products, and more particularly to bodyboards for riding on waves such as ocean surf.
Bodyboards are flotation amusement devices for riding waves. They are similar to surfboards, with the major difference being that bodyboards are shorter, lighter and generally more flexible than surfboards. In form, a bodyboard is a contoured, elongated, semi-rigid foam plank having a top riding surface and a bottom surface covered with a plastic bottom skin which is generally slick and somewhat stiff for planing on water.
Speed and maneuverability are important attributes of bodyboards. The bottom skin which forms the bottom surface of a bodyboard is made from a relatively hard, non-foam, plastic material which is employed partly because it is "slippery" and helps reduce drag. Low bottom surface drag is especially desirable because it increases the speed of the bodyboard and helps when performing the tricks and maneuvers which make bodyboarding the fast-paced exhilarating sport it has become.
Even a bottom surface which is made of flat, slick plastic does produce noticeable drag between the board and water which can slow the bodyboard. One theory to explain the drag is that the flat, wet bottom surface includes water molecules which cling to the board, causing shear between the moving and non-moving water molecules as the board passes through the water. The drag produced is not great, but does result in a noticeable, effect on bodyboard performance. Bodyboard riders describe the characteristic feel or sensation of a typical prior art board passing through the water as "carving" or "slicing" through the water, as opposed to frictionless movement over the water.
It would be advantageous to further enhance the performance of bodyboards by reducing bottom surface drag. In particular, it would be advantageous to reduce bottom surface drag on bodyboards, thereby improving the speed and performance of bodyboards, by employing a new type of textured bottom surface skin. It would also be advantageous to provide a method of producing the improved, drag-reducing bottom skin for bodyboards.
Accordingly, the present invention provides an improved bottom surface for bodyboards of the type used to ride on waves such as ocean surf. Such bodyboards are in the form of an elongate, substantially planar board having a foam core, a top surface for supporting a rider, and a bottom surface for planing on water. The bottom surface of the board, incorporating the improved skin of the present invention, comprises a plurality of discreet depressions formed on the bottom surface of the board, the number of such depressions exceeding approximately 50 depressions over selected regions of the bottom surface of the board. The depressions enhance the planing of the bodyboard on water. At least one theory explaining the enhancement produced by the depressions is that the textured bottom surface causes air bubbles to become trapped between the bottom surface of the board and the water, resulting in "air lubrication" of the bottom surface as the bodyboard moves through the water.
The present invention further includes an improved bottom skin for use on bodyboards of the type which are in the form of an elongate, semi-rigid foam plank having a top riding surface for supporting a rider and a bottom surface for planing on water. The bottom skin of the bodyboard substantially covers the bottom of the board and forms its bottom planing surface. The improved bottom skin comprises an expanse of thermoplastic sheet material in which a plurality of discreet depressions are formed. The density of depressions preferably exceeds approximately 8 depressions per-square-foot.
The invention further includes a method of forming an improved bottom skin for use on bodyboards used to ride on waves such as ocean surf. The bottom skin is formed from an expanse of thermoplastic sheet material overlying an adjacent layer of semi-rigid foam. Steps in the method comprise heating the thermoplastic sheet material until the material is deformable or moldably plastic. A subsequent step is impressing the sheet material, while in the moldably plastic state, with a plurality of convex, depression-forming projections or elements. The density of projections used in the impressing step exceeds approximately 8-projections per-square-foot and results in a corresponding reverse-pattern which includes a plurality of discreet depressions on the bottom skin. Finally, the thermoplastic bottom skin sheet material is allowed to cool until it has set with the projections formed therein.